After making almost everything on my last build, I've learned that there is no shame in buying where it makes sense. Brackets and axle trusses are on that list. So are corner guards. There are definitely things that are worth buying. The real lesson is to not make plans until you have parts in hand. Even the most reliable vendors let this industry down from time to time.

I agree with every word of this. I thought it'd be cool to make all my own stuff, but in the end it cost me just as much money and 10x as much time. But if it'll save you 3 weeks that you'd otherwise be waiting for parts, go for it. Some flat plate, a couple poly bushings, a few bolts, and either tube or more flat plate and you've got yourself motor mounts.